And Then There Were None is a mystery novel by the English writer Agatha Christie, who described it as the most difficult of her books to write. It was first published in the United Kingdom by the Collins Crime Club on 6 November 1939, as Ten Little Niggers, after an 1869 minstrel song that serves as a major plot element. The US edition was released in January 1940 with the title And Then There Were None, taken from the last five words of the song. Successive American reprints and adaptations use that title, though American Pocket Books paperbacks used the title Ten Little Indians between 1964 and 1986. UK editions continued to use the original title until 1985.

Mystery is a fiction genre where the nature of an event, usually a murder or other crime, remains mysterious until the end of the story. Often within a closed circle of suspects, each suspect is usually provided with a credible motive and a reasonable opportunity for committing the crime. The central character is often a detective, who eventually solves the mystery by logical deduction from facts presented to the reader. Some mystery books are non-fiction. Mystery fiction can be detective stories in which the emphasis is on the puzzle or suspense element and its logical solution such as a whodunit. Mystery fiction can be contrasted with hardboiled detective stories, which focus on action and gritty realism.